Uninterruptible power source improvements for protection from common grid problems combined with ultra fast switching

ABSTRACT

Improvements are disclosed to a basic offline/standby UPS that keep its high standby efficiency while improving it electrical performance to match a online/double conversion UPS. One such improvement comprises a method for modifying a basic standby power system (SPS) to correct a common grid problem, the method comprising: providing an offline/standby uninterruptible power source (UPS) with a line conditioning inverter which contains a high speed voltage controlled pulse-width modulation (PWM) inverter; detecting and measuring a line voltage using a phase and filter controller having a high speed analog-to-digital converter (ADC); comparing the measured line voltage to an expected line voltage; and detecting any voltage spike or sustained overvoltage deviation from a sinusoidal waveform and sending it to the line conditioning inverter for reducing the load voltage back to nominal.

TECHNICAL FIELD

The present disclosure is generally related to uninterruptible power source (UPS) improvements for protection from grid problems.

SUMMARY

Embodiments of the invention relate to modification to basic offline/standby UPS systems (Standby Power System, SPS), as illustrated in FIG. 1. In some embodiments, the switchover time can be reduced nearly instantaneously from multiple half wave AC power cycles, 15 to 35 milliseconds, to no half wave power cycle loss. In addition, some embodiments provide an “electrical firewall” between the incoming utility power and sensitive electronic equipment. This improves the SPS performance to where it can be used in place of the higher cost online/double-conversion UPS (FIG. 2) or delta conversion online UPS (FIG. 3) in environments where electrical isolation is necessary, or for equipment that is very sensitive to power fluctuations. The system maintains an insignificant power consumption when in the offline/standby state. Some embodiments of the present application involve an improvement in the SPS system to provide the same features, no momentary power dropout and electrical isolation, as the online/double-conversion UPS or delta conversion online UPS, but without the undesirable aspects of high cost, and increased power consumption of 15 to 25%.

Referring to FIG. 1, the offline/standby UPS (SPS) offers only the most basic features including surge protection via surge protector 10, passive line filtering via noise filter 20, and battery backup via battery charger 30, battery 40 and DC-AC converter 50. The protected equipment is normally connected directly to incoming utility power via surge protector 10, noise filter 20 and transfer switch 60. When the incoming voltage falls below or rises above a predetermined level as detected via voltage monitor 70, the SPS turns on its internal DC-AC inverter 50, which is powered by internal storage battery 40. The SPS then mechanically switches (via transfer switch 60) the connected equipment to an output of the DC-AC inverter 50. The switchover time can be as long as 35 milliseconds, depending on the amount of time it takes the SPS to detect the lost utility voltage via voltage monitor 70 and the switchover time of the mechanical switch 60. The intended use of the SPS is to power certain equipment, such as a personal computer, that typically has substantial internal energy storage in its power supply, so that backup power is switched on without any objectionable dip or brownout.

The SPS is frequently operated in standby mode (power supplied directly from the grid) with its DC-AC inverter 50 off. Having no operational inverter provides exceptionally low operating cost. However, connecting directly to the grid subjects the equipment to common grid problems such as: (i) voltage spike or sustained overvoltage, (ii) momentary or sustained undervoltage, (iii) noise, defined as a high frequency transient or oscillation, usually injected into the line by nearby equipment, (iv) Instability of the mains frequency, and (v) harmonic distortion (i.e., a departure from the ideal sinusoidal waveform expected on the line).

When SPS switchover occurs, switching the SPS from standby to active mode, the SPS turns on its internal DC-AC inverter 50 circuitry, which is powered from an internal storage battery 40. The SPS then mechanically switches (via transfer switch 60) the connected equipment on to its DC-AC inverter 50 output. Switchover can take up to 35 milliseconds, leaving the electrical equipment operating with the detected grid problem and switch noise from the mechanical transfer switch 60. Embodiments of the application correct the switchover and grid problems within the same power cycle and help retain lower power consumption when operating in standby mode.

Throughout the present teachings, any and all of the features and/or components disclosed or suggested herein, explicitly or implicitly, may be practiced and/or implemented individual and/or in any combinations of two, three, or more thereof, whenever and wherever appropriate as understood by one of ordinary skill in the art. The various features and/or components disclosed herein are all illustrative for the underlying concepts, and thus are non-limiting to their actual descriptions. Any means for achieving substantially the same functions are considered as foreseeable alternatives and equivalents, and are thus fully described in writing and fully enabled. The various examples, illustrations, and embodiments described herein are by no means, in any degree or extent, limiting the broadest scopes of the claimed inventions presented herein or in any future applications claiming priority to the instant application.

Disclosed herein is an offline/standby system (SPS) and methods for achieving online/double-conversion system having steady power characteristics and “electrical firewall” protection without the high cost and power losses of the online/double-conversion system.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be more readily appreciated upon review of the detailed description of its various embodiments, described below, when taken in conjunction with the accompanying drawings.

FIG. 1 is a block diagram of a basic offline/standby UPS and its components.

FIG. 2 is a block diagram of an online/double conversion and its components.

FIG. 3 is a block diagram of a delta conversion online UPS and its components.

FIG. 4 is a block diagram of an offline/standby UPS with line conditioning inverter and its components.

The drawings are described in greater detail in the description and examples below. The drawings are not intended to be exhaustive or to limit the various embodiments to the precise form disclosed. It should be understood that embodiments can be practiced with modification and alteration.

DETAILED DESCRIPTION

The details of some example embodiments of the methods and systems of the present disclosure are set forth in the description below. Other features, objects, and advantages of the disclosure will be apparent upon examination of the following description, drawings, examples and claims. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims.

FIG. 2 is a block diagram of an online/double conversion and its components, including a rectifier 210, battery 220, and inverter 230, whereas FIG. 3 is a block diagram of a delta conversion online UPS and its components, including delta transformer 310, rectifier 320, battery 330, and inverter 340.

FIG. 4 is a block diagram illustrating an offline/standby UPS with line conditioning inverter which allows “electrical firewall” features. The offline/standby UPS with line conditioning inverter includes phase and filter control 410 and line conditioning inverter 420. A known “electrical firewall” common grid problem is voltage spike or sustained overvoltage. This problem is detected with the phase & filter controller 410, which has a high speed analog-to-digital converter (ADC) that measures the line voltage and compares it to the expected value. Any voltage spike or sustained overvoltage deviation from the sinusoidal waveform is sent to the line conditioning inverter 420, which contains high speed voltage controlled PWM inverter. The PWM inverter may put a voltage in the opposite direction as the voltage spike or sustained overvoltage. Since the line conditioning inverter is in series with the grid voltage, the load voltage (the sum of the two, grid and line conditioning inverter) may reduce the load voltage back to nominal.

When the line conditioning inverter 420 is operating to reduce voltage spikes or sustained overvoltage, it is not operating as an inverter, but as a rectifier charging the batteries. If the battery 440 is not 100% charged, the incremental power may charge the battery 440 until it is 100% charged. If the battery is 100% charged, to keep from overcharging the battery, the DC-AC inverter 450 may go from the off state to the on state and provide the incremental power to the load in parallel with the AC output of the line conditioning inverter 420, using up the incremental power being supplied to the battery 440.

Another known “electrical firewall” common grid problem is momentary or sustained undervoltage. Like the overvoltage problem this issue is detected with the phase & filter controller 410, which has a high speed ADC that measures the line voltage and compares it to the expected value. Any momentary or sustained undervoltage deviation from the sinusoidal waveform is sent to the line conditioning inverter 420, which contains the high speed voltage controlled PWM inverter. The PWM inverter may put a voltage in the same direction as the momentary or sustained undervoltage. Since the line conditioning inverter is in series with the grid voltage, the load voltage (the sum of the two, grid and line conditioning inverter) may reduce the load voltage back to nominal.

When the line conditioning inverter is operating to correct momentary or sustained undervoltage, it is discharging the batteries by the incremental power it needs to boost the voltage. The battery charger 430 may then turn on and provide incremental power to charge the batteries until they are 100% charged.

Noise can be defined as a high frequency transient of oscillation, usually injected into the line by nearby equipment. Just like the overvoltage and under voltage cases above, any voltage deviation within the bandwidth of the phase & filter controller 410 and line conditioning inverter 420 control loop from nominal grid voltage may be canceled out. Accordingly, the phase & filter controller 410 and line conditioning inverter 420 act as a noise filter.

Instability of the mains frequency, phase noise, or jitter can be seen as a voltage deviation. Just like voltage deviation, instability of the mains frequency may be removed by the phase & filter controller and line conditioning inverter control loop.

Harmonic distortion can be defined as a departure from the ideal sinusoidal waveform expected on the line. Just like the overvoltage and undervoltage cases above, voltage deviation from harmonic distortion may be corrected within the phase & filter controller and line conditioning inverter control loop.

Still referring to FIG. 4, when the grid reaches either its high or low switchover voltage, the UPS switches from its offline/standby state to its online state. This transition occurs very fast, more than 100 times faster than the line frequency itself. Unlike the basic UPS that switches a mechanical relay, the line conditioning inverter 420 and inverter 450 are able to operate in parallel sharing the load. Accordingly, the UPS transitions from offline state to online state by turning on the battery power inverter 450, transitioning the load current from the line conditioning inverter 420 to the inverter 450, and turning off the line conditioning inverter 420 to prevent grid islanding.

Retaining a lower power consumption when operating in standby mode is desirable because a UPS spends more than 99.999 percent of it time with the grid close to its nominal voltage. Accordingly, to achieve the lowest possible operating cost, this is the state where UPS power consumption makes the most difference. There are two features designed into the offline/standby UPS with line conditioning inverter (FIG. 4) that establish lower consumption than the online/double conversion UPS (FIG. 2) or the delta conversion (FIG. 3). First, the offline/standby UPS with line conditioning inverter turns off its “main inverter” 450 when in offline/standby mode. Second, the line conditioning inverter 420 is at least 5 times smaller in power output than the main inverter at the same efficiency. It can be sized 5 times smaller in power output because 80% or more of the load's power comes from the grid, not the inverter itself.

Typical UPS inverters are 93 to 95% efficient, given the same efficiency of the lower power line conditioning inverter 420 (i.e., the only inverter on while in standby mode), the efficiency of the overall UPS system is 5 times higher (i.e., 98 to 99%). This is because the line conditioning inverter 420 operates at only 20% of the power of the online inverter. By comparison, the efficiency when in offline/standby mode of offline/standby UPS with line conditioning inverter (FIG. 4) is approximately two times better than delta conversion (FIG. 3), 98.5% versus 97%.

As used herein, the term component might describe a given unit of functionality that can be performed in accordance with one or more embodiments of the present application. As used herein, a component might be implemented utilizing any form of hardware, software, or a combination thereof. For example, one or more processors, controllers, logical components, software routines or other mechanisms might be implemented to make up a component. In implementation, the various components described herein might be implemented as discrete components or the functions and features described can be shared in part or in total among one or more components. In other words, as would be apparent to one of ordinary skill in the art after reading this description, the various features and functionality described herein may be implemented in any given application and can be implemented in one or more separate or shared components in various combinations and permutations. Even though various features or elements of functionality may be individually described or claimed as separate components, one of ordinary skill in the art will understand that these features and functionality can be shared among one or more common software and hardware elements, and such description shall not require or imply that separate hardware or software components are used to implement such features or functionality.

Various embodiments have been described with reference to specific exemplary features thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the various embodiments as set forth in the appended claims. The specification and figures are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Although described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the present application, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present application should not be limited by any of the above-described exemplary embodiments.

Terms and phrases used in the present application, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.

The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “component” does not imply that the components or functionality described or claimed as part of the component are all configured in a common package. Indeed, any or all of the various components of a component, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.

Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration. 

What is claimed is:
 1. A method for modifying a basic standby power system (SPS) to correct a common grid problem, the method comprising: providing an offline/standby uninterruptible power source (UPS) with a line conditioning inverter which contains a high speed voltage controlled pulse-width modulation (PWM) inverter; detecting and measuring a line voltage using a phase and filter controller having a high speed analog-to-digital converter (ADC); comparing the measured line voltage to an expected line voltage; and detecting any voltage spike or sustained overvoltage deviation from a sinusoidal waveform and sending it to the line conditioning inverter for reducing the load voltage back to nominal.
 2. The method of claim 1, wherein reducing the load voltage back to nominal comprises sending a voltage in the opposite direction of the voltage spike or sustained overvoltage.
 3. The method of claim 2, wherein the line conditioning inverter functions as a rectifier by charging a battery of the SPS while reducing the load voltage back to nominal.
 4. The method of claim 1, wherein reducing the load voltage back to nominal comprises the phase and filter controller and line conditioning inverter acting as a noise filter.
 5. The method of claim 1, wherein reducing the load voltage back to nominal comprises removing instability of a mains frequency.
 6. The method of claim 1, wherein reducing the load voltage back to nominal comprises correcting voltage deviation from harmonic distortion.
 7. The method of claim 1, wherein the line conditioning inverter is at least 5 times smaller in power output than a main inverter of the SPS at the same efficiency.
 8. The method of claim 1, wherein the line conditioning inverter operates at only 20% of the power of a main inverter of the SPS at the same efficiency.
 9. A method for modifying a basic standby power system (SPS) to correct a common grid problem, the method comprising: providing an offline/standby uninterruptible power source (UPS) with a line conditioning inverter which contains a high speed voltage controlled pulse-width modulation (PWM) inverter; detecting and measuring a line voltage using a phase and filter controller having a high speed analog-to-digital converter (ADC); comparing the measured line voltage to an expected line voltage; and detecting any momentary or sustained undervoltage deviation from a sinusoidal waveform and sending it to the line conditioning inverter for increasing the load voltage back to nominal.
 10. The method of claim 9, wherein increasing the load voltage back to nominal comprises sending a voltage in the same direction of the momentary or sustained undervoltage.
 11. The method of claim 9, wherein increasing the load voltage back to nominal comprises the phase and filter controller and line conditioning inverter acting as a noise filter.
 12. The method of claim 9, wherein increasing the load voltage back to nominal comprises removing instability of a mains frequency.
 13. The method of claim 9, wherein reducing the load voltage back to nominal comprises correcting voltage deviation from harmonic distortion.
 14. The method of claim 9, wherein the line conditioning inverter is at least 5 times smaller in power output than a main inverter of the SPS at the same efficiency.
 15. The method of claim 9, wherein the line conditioning inverter operates at only 20% of the power of a main inverter of the SPS at the same efficiency. 